A 'we are all one' scenario would have to be defined first and then go from there.
I don't tend to use these terms myself, but my view or understanding is that it's basically about relationship.
We are all in relationship on the level of being human at least, and the things we have in common as humans.
It would be deeper according to groupings, and further in friends, partnership etc.

Looking at the question again, and no matter the definition of 'we are all one', it seems to be mostly just asking about others judgeing someone else for judgeing...
So maybe it could be presented something like this:

A judges B. C judges A for judgeing B.

Is C in a position to judge A?
- or -
Is C equally guilty of the type of judgement it accuses A of?

I don't want to misrepresent it though, so please correct or disagree as appropriate. It's just an attempt to clarify/simplify.